New designer drugs, such as mephedrone, have played a role in 42 deaths in the past two years. Photograph: Jon Enoch/eyevine

All "legal highs" or designer drugs such as mephedrone – now banned – that mimic the effects of established illegal drugs, should be automatically banned, according to the government's official advisers on illicit substances.

The Advisory Council on the Misuse of Drugs (ACMD) has said the government needs to adopt a much tougher US-style system of controls. The recommendation comes after claims that the more recently available designer drugs have played a role in 42 deaths in the past two years.

Prof Les Iversen, the ACMD chair, said tougher controls were needed to prevent suppliers from simply tweaking the chemistry of newly banned substances to get around the law.

More than 40 new legal highs have been identified in the past two years, often emerging from laboratories in south-east Asia, where chemists design new compounds that replicate the effects of already banned substances such as cannabis, amphetamine and ecstasy.

Many are marketed through online sites offering the substances as "plant food" or "not fit for human consumption", but their purpose is often transparent.

Iversen said the Polish government had recently taken bold action in closing down hundreds of "head shops" similar to those found in Camden market, north London, as well as automatically banning new legal highs.

The British government has responded by introducing a system of temporary bans on each new substance as soon as it emerges; parliamentary approval is needed for each banning order before detailed tests are done to determine the level of harm of the substance.

But the ACMD says it necessary to go further and adopt a system similar to the US analogue act whereby substances bearing a chemical similarity to existing controlled substances, such as amphetamines or the active ingredient in cannabis, are banned. "The system of temporary bans is not a winning strategy because new substances will always continue to emerge," said Iversen.

"Just because it is advertised as a legal high does not mean it is safe. Users are playing a game of Russian roulette when they buy something described as research drugs. They are researching the effects on themselves. It is a totally unregulated market. We are not seeing just a nice party drug but something that can kill."

The government's drug advisers also want to see existing legislation used more effectively to prevent legal highs being falsely advertised as bath salts or plant food, and to shift the burden of proof on to suppliers to show their products are safe for human consumption.

Iversen said figures from the the National Programme on Substance Abuse Deaths, based at St George's hospital, south London, had logged 127 suspected cases of deaths in Britain that had links with mephedrone over the past two years. Forty-two cases were confirmed as having a link with mephedrone, although none had given the drug as the direct cause of death. So far, 29 of the 127 suspected cases have been shown to have no connection with mephedrone.

The ACMD report says a different type of drug dealer has emerged. Entrepreneurs are seizing upon the business opportunities. "Many people importing these new substances appear to have had no previous involvement in the illicit drug trade and are just in it to make a quick buck. They have included students who have set up websites to supply nationally and who also supply the local student population."

These dealers ensure that the market is quickly saturated with the new drug, the report adds.

But Roger Howard, of the UK Drug Policy Commission thinktank, warned that the tough approach was unlikely to work. "Analogue controls would save politicians from the pressure to do something when the new drugs appear on the market. But they wouldn't solve the real problem."

He said it was increasingly difficult for the police to identify the rapidly growing numbers of psychoactive drugs on the market.

"Controlling even more drugs through the drug laws doesn't do anything to help that nor to prevent the harm that might emerge. We need to think differently, about using other controls to bring some discipline to an unregulated market."